Electric buzzer

ABSTRACT

An electric coil is wound on a plastic bobbin, the latter having a central sleeve within which a magnetic core is slideably positioned. One end of the sleeve is closed and projects beyond the coil. An inverted cup-shaped housing surrounds the coil and bobbin and has a central opening through which the closed end of the sleeve projects. The core projects into the closed end of the sleeve beyond the margin of the opening in the housing to augment the magnetic coupling between the housing and the core. The open end of the housing is attached to a support bracket of magnetic material, there being a spring between the bracket and bobbin normally urging the core toward the closed end of the sleeve.

United States Patent 1 Sehantz Dec. 16, 1975 1 1 ELECTRIC BUZZER [76]Inventor: Spencer C. Schantz, 16608 W.

Rogers Drive, New Berlin, Wis. 53151 22 Filed: Feb. 6, 1975 21 Appl. No;547,411

[56] References Cited UNITED STATES PATENTS 7/1954 Meleski 340/39610/1970 Dolter 340/396 X Primary ExaminerHarold I. Pitts Attorney,Agent, or FirmArthur L. Morsell, Jr.

[57] ABSTRACT An electric coil is wound on a plastic bobbin, the latterhaving a central sleeve within which :1 magnetic core is slideablypositioned. One end of the sleeve is closed and projects beyond thecoil. An inverted cupshaped housing surrounds the coil and bobbin andhas a central opening through which the closed end of the sleeveprojects. The core projects into the closed end of the'sleeve beyond themargin of the opening in the housing to augment the magneticcoupling'between the housing and the core. The open end of the housingis attached to a support bracket of magnetic material, there being aspring between the bracket and bobbin normally urging the core towardthe closed end of the sleeve.

9 Claims, 3 Drawing Figures US. Patent Dec. 16, 1975 3,927,403

ELECTRIC BUZZER BACKGROUND OF THE INVENTION SUMMARY: or THE INVENTION 5In the buzzer of this invention, the bobbin has a cen-.

tral co re-receiving sleeve which is closed;at one end. The closed endof the, sleeve projects beyond the electric coil wound on the bobbin. v

An inverted cup-shaped housing surrounds the bobbin and coil and has acentral opening in the closed end thereof through which the closed endof I the .sleeve 7 projectsfThe core projects beyond the margin of theopening in the housing to improve themagnetic coupling between the coiland the core. The open end of the housing is attached to a supportbracket made of magnetic material, there being a spring between thebracket and bobbin normally urging the core toward the closed end of thesleeve.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the preferredembodiment of the invention.

FIG. 2 is a longitudinal sectional view taken on the line 22 of FIG. 1.

FIG. 3 is a sectional view taken on the line 33 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodimentincludes a bobbin 10 (FIG. 2) which is made of a suitable non-magneticmaterial such as nylon or the like. Bobbin 10 has a central sleeve 12and two annular flanges l4 and 16 which are axially spaced apart onsleeve 12 and act as retaining walls for an electric coil 18 wound onsleeve 12 between flanges 14 and 16. A pair of electrical conductors 20(FIG. I) are attached to the ends of coil 18 and terminate in terminals22 for connection to a switchable source of alternating current forenergizing the buzzer. The upper end 24 of sleeve 12 projects beyondflange 14 and beyond coil 18, and is closed at 26 to limit the upwardmovement of a core 28 which is made of magnetic material and which isdimensioned to slideably fit within the interior of sleeve 12. The lowerend of sleeve 12 is open. Sleeve 12, flanges 14 and 16, projecting end24 and end closure 26 are all an integral part of bobbin 10, which canbe formed by known injection molding techniques.

Bobbin l0, coil 18, and core 28 are contained within a housing 30 whichis preferably but not necessarily made of magnetic material and shapedlike an inverted cup. The lower end of housing 30 is open, and the upperend is closed at 32 and provided with a central opening 34 through whichthe upper end 24 of sleeve 12 projects. The upper end portion 35 of core28 projects within the upper end 24 of sleeve 12 beyond the margin ofopening 34, to enhance the magnetic coupling between housing 30 and core28. When core 2 28 is .within and not below the margin of opening. 34,the magnetic reluctance therebetween is at a minimum value. y

. At'its lower open end, housing 30 has stake portions 36 extendingdownwardly a short distance therefrom and engagingmatching openings in.a banjo-shaped mounting bracket38 which is fastened thereby over theopen end of housing 30. Mounting bracket 38 is made of magnetic materialto complete the magnetic circuit formed by coil 30 and core 35. It isslotted at 40 (FIG. 1) for convenient insertion under a mounting screw(not shown). I i

Thebobbin flange 14 is preferably provided with raised projecting means14a near its outer periphery.

This may take theform= of ,two or more raised dots spaced symmetricallyabout the axis of thebobbin, or

may take'the form of a circular raised rib. When the housing 30 isstaked tothe mounting bracket 38 by means of the stakes 36, theprojecting means 1421 engage the underside of the top 32 of the housing30 to cause the outer peripheral portion of the flange 14 of the bobbinto be deflected-downwardly, as. shown in FIG. 2. Thiseliminateslooseness of the bobbin26 in the assembly which might be caused bytolerance buildup. The deflection of the outer peripheral portion of theflange l4 compresses the coil 18 in an amount sufficient to absorbtolerances of piece parts.

The end closure 26 of sleeve 24 has a depression 26a to providesufficient clearance for any burr 28a which might be left on the end ofthe core portion 35. Where metal items of this type are cut off by ascrew machine operation, a burr such as the burr 28 is generally left,and, by having the recess 26a, the necessity of removing these burrs iseliminated.

The underside of flange 16 has diametrically aligned grooves 42 and 44(FIG. 3) to receive a leaf spring 46, which is supported at its ends bymounting bracket 38 and urges core 28 upwardly toward the closed end 26of sleeve 12. When coil 18 is energized by alternating current, core 28vibrates axially within sleeve 12, moving spring 46 and causing thelatter to strike mounting bracket 38, and then moving upwardly again ineach half cycle of the alternating current as the magnetic field buildsup to a maximum and then drops to zero, thereby producing a buzzingsound.

Core 28 is preferably long enough so that its upper end 35 does not dropbelow the level of the opening 34 in housing 30 when core 28 isdrawndownwardly by the magnetic field. This maximizes the magneticcoupling between housing 30 and core 28, if the housing is magnetic, andthereby maximizes the buzz intensity produced by any given A.C. currentflow through coil 30, or else minimizes the current required to producea given buzz intensity. If the housing is not magnetic, such as plastic,the magnetic coupling is still enhanced by the length of core protrudingbeyond the coil. The mounting bracket 38 serves not only as a closurefor the open ends of both the sleeve 12 and housing 30, but also servesas a support for the entire buzzer and as a sounding board for thevibration of core 28. This simplifies the structure of the buzzer andsubstantially reduces its cost.

An alternate construction may eliminate housing 30, with bobbin 10 beingsuitably attached to bracket 38.

What I claim:

1. An electric buzzer comprising a bobbin of nonmagnetic material havinga central sleeve portion with a bore, an electric coil wound on saidbobbin around said sleeve portion, one end of said sleeve portionprojecting beyond an end of the coil and being closed to close said endof the bore, and the other end being open, a magnetic core slideablymounted in the bore of said sleeve portion and having an end projectinginto the projecting portion of the sleeve, a bracket of magneticmaterial attached to the end of the bobbin opposite the end having theprojecting sleeve portion and closing the open end of the sleeve bore,and spring means normally urging said core toward the closed end of thesleeve bore.

2. An electric buzzer as claimed in claim 1 in which there is aninverted cup-shaped housing having a portion surrounding the bobbin andhaving one end with a central opening through which said projectingsleeve portion projects and having its other end open, and wherein thebracket of magnetic material is connected to the open end of the housingto close said end.

3. The buzzer of claim 1 wherein said spring means is mounted betweensaid bracket and said core.

4. The buzzer of claim 1 wherein the bobbin includes two spaced apartannular flanges on said sleeve, said coil being wound on said sleevebetween said flanges,

4 one of said flanges being adjacent the open end of said sleeve andhaving aligned grooves accommodating said spring means.

5. The buzzer of claim 1 wherein said core is long enough to alwaysproject beyond the coil.

6. The buzzer of claim 2 wherein there are staking members projectingfrom the open end of said housing, and wherein there are openingsin-said bracket receiving said staking members, said staking membersbeing staked to hold the assembly together.

7. The buzzer of claim 1 wherein the bobbin flange which is adjacent theopen end of the sleeve is relatively thick and fits against the bracket,wherein the aligned grooves of said flange face said bracket, andwherein there is a leaf spring accommodated in said grooves and havingan upwardly bowed portion engaging the adjacent end of the core to actthereon.

8. The electric buzzer claimed in claim 2 wherein the housing is made ofmagnetic material.

9. The electric buzzer claimed in claim 2 wherein the core is longenough to always project beyond the margin of said central opening ofthe housing.

1. An electric buzzer comprising a bobbin of non-magnetic materialhaving a central sleeve portion with a bore, an electric coil wound onsaid bobbin around said sleeve portion, one end of said sleeve portionprojecting beyond an end of the coil and being closed to close said endof the bore, and the other end being open, a magnetic core slideablymounted in the bore of said sleeve portion and having an end projectinginto the projecting portion of the sleeve, a bracket of magneticmaterial attached to the end of the bobbin opposite the end having theprojecting sleeve portion and closing the open end of the sleeve bore,aNd spring means normally urging said core toward the closed end of thesleeve bore.
 2. An electric buzzer as claimed in claim 1 in which thereis an inverted cup-shaped housing having a portion surrounding thebobbin and having one end with a central opening through which saidprojecting sleeve portion projects and having its other end open, andwherein the bracket of magnetic material is connected to the open end ofthe housing to close said end.
 3. The buzzer of claim 1 wherein saidspring means is mounted between said bracket and said core.
 4. Thebuzzer of claim 1 wherein the bobbin includes two spaced apart annularflanges on said sleeve, said coil being wound on said sleeve betweensaid flanges, one of said flanges being adjacent the open end of saidsleeve and having aligned grooves accommodating said spring means. 5.The buzzer of claim 1 wherein said core is long enough to always projectbeyond the coil.
 6. The buzzer of claim 2 wherein there are stakingmembers projecting from the open end of said housing, and wherein thereare openings in said bracket receiving said staking members, saidstaking members being staked to hold the assembly together.
 7. Thebuzzer of claim 1 wherein the bobbin flange which is adjacent the openend of the sleeve is relatively thick and fits against the bracket,wherein the aligned grooves of said flange face said bracket, andwherein there is a leaf spring accommodated in said grooves and havingan upwardly bowed portion engaging the adjacent end of the core to actthereon.
 8. The electric buzzer claimed in claim 2 wherein the housingis made of magnetic material.
 9. The electric buzzer claimed in claim 2wherein the core is long enough to always project beyond the margin ofsaid central opening of the housing.